fun main() {
    //set里面没有重复元素
    val set = setOf("jason", "jack", "jacky", "jack")
    println(set.elementAt(2))


    val mutableSet = mutableSetOf("jason", "jack", "jacky", "jack")
    mutableSet += "jimmy"

    //list转set去重
    val list = listOf("jason", "jack", "jacky", "jack").toSet().toList()
    println(list)

    println(listOf("jason", "jack", "jacky", "jack").distinct())
}